1. Field of the Invention
The present invention relates to a microwave oven combined with a television (hereinafter referred to as "TV"), and more particularly to a cooking state displaying apparatus and method which can selectively display the cooking state of a microwave oven on the TV screen.
2. Description of the Prior Art
The conventional cooking state displaying apparatus is generally installed on the front side of a microwave oven and visually displays a cooking state or completion to a user.
As shown in FIG. 1, the conventional cooking state displaying apparatus comprises a microcomputer 10 for controlling the operation of a microwave oven, a cooking state sensing section 20 for sensing a cooking state in order to provide the sensed information to microcomputer 10, a display section 30 for displaying a cooking state in accordance with the sensed information from sensing section 20 under the control of microcomputer 10, and a buzzer driving section 40 for indicating the completion of cooking under the control of microcomputer 10.
FIG. 2 is a detailed circuit diagram of the conventional cooking state displaying apparatus for a microwave oven. Referring to FIG. 2, cooking state sensing section 20 comprises a cooking state sensor RS and a voltage dividing resistor R14, which are connected to analog/digital conversion input terminal AD of microcomputer 10. Moreover, display section 30 comprises transistor arrays 31 and 32, respectively connected to first and second LED (Light Emitting Diode) driving terminals P10 to P16, P20 and P21, a plurality of current limiting resistors R7 to R13, and LED displayers 33 and 34 for displaying cooking state and completion, being driven by the outputs of first and second LED driving terminals P10 to P16, P20 and P21. And, buzzer driving section 40 comprises transistors Q1 and Q2, whose bases are respectively connected to control terminal CL and buzzer control terminal BZ of microcomputer 10, a buzzer 41 driven by transistors Q1 and Q2, and a plurality of bias transistors R1 to R6.
Meanwhile, as a cooking state sensor RS, a gas sensor for sensing the amount of gas generated from food during cooking, a humidity sensor for sensing the variation of humidity in a heating cavity of a microwave oven, and a temperature sensor for sensing the variation of temperature of food or in the heating cavity are usually used.
The operation of the conventional apparatus constructed as above will be explained as follows.
The resistance value of sensor RS in sensing section 20 varies according to cooking state. In the case of temperature sensor, the temperature varies in accordance with cooking-state and the variation of temperature can be detected as that of resistance value of the sensor. So, output voltage of sensor RS corresponds to the value of [the supply voltage Vcc.times.load resistance R14]+[sensor resistance RS+load resistance R14] and is supplied to analog/digital conversion input terminal AD of microcomputer 10 to be digital-converted. Then, microcomputer 10 determines a cooking state by the output value of sensor.
The current cooking state determined as above is displayed in characters, figures and/or graphics. That is, microcomputer 10 provides cooking state displaying signals through first and second LED driving terminals P10 to P16, P20 and P21. And those output signals are combined by transistor arrays 31 and 32 and then are supplied to LED displayers 33 and 34. Therefore, the cooking state can be displayed.
For example, if the output of terminal P10 in microcomputer 10 becomes "low", the output of the corresponding transistor in transistor array 31 becomes "high" and a positive voltage is sequentially applied to corresponding LEDs in LED displayers 33 and 34. At the same time, if the output of terminal P20 in microcomputer 10 becomes "high" the output of the corresponding transistor in transistor array 32 becomes "low". Accordingly, the LED in LED displayer 31 to which the positive voltage is applied is lit up so that a cooking state can be displayed in characters or figures.
Meanwhile, when cooking is completed, the output of buzzer control terminal BZ in microcomputer 10 becomes "high". Accordingly, transistors Q2 and Q1 are sequentially turned on and thus voltage Vcc having passed through resistor R6 is applied to buzzer 41. Then, a buzzer sound for indicating the completion of cooking is generated.
However, since the conventional displaying apparatus is installed on the front side of a microwave oven, a user may not realize the cooking state or completion while the user watches television or is otherwise occupied. Moreover, even though a user is separated from a microwave oven during cooking, a cavity lamp for indicating a cooking state is still on so that power is unnecessarily consumed.